Plasma reflection in multigrain layers of narrow-bandgap semiconductors

Qualitatively similar spectral characteristics of plasma-resonance reflection in the region of 15–25 $\mu$m were obtained for layers of electrodeposited submicron particles of InSb, InAs, and GaAs and plates of these semiconductors ground with M1-grade diamond powder. The most narrow-bandgap semiconductor InSb (intrinsic absorption edge $\sim$7 $\mu$m) is characterized by an absorption band at 2.1–2.3 $\mu$m, which is interpreted in terms of the model of optical excitation of electrons coupled by the Coulomb interaction. The spectra of a multigrain layer of chemically deposited PbS nanoparticles (50–70 nm) exhibited absorption maxima at 7, 10, and 17 $\mu$m, which can be explained by electron transitions obeying the energy-quantization rules for quantum dots.